A wireless communications network may include a plurality of devices—e.g., access points (APs), with each respective access point serving a respective plurality of stations (STAs). For example, in a wireless local area network (WLAN) under the IEEE802.11 standard (commonly referred to as “Wireless Fidelity” or “WiFi”), a grouping including one access point and its associated stations may be referred to as a “basic service set” (BSS). Such a network may include multiple BSSs.
Each access point can set its own transmit power level, up to any regulatory maximum that may be imposed (these may differ by jurisdiction). The access point also can control the transmit power levels of its associated stations through control messages (e.g., “Beacon” or “Probe” messages under the IEEE802.11 standard).
However, in practice, access points and associated stations usually operate at the maximum permitted power level at all times, even on links involving close physical proximity with good signal characteristics. From the perspective of the access point, the access point “wants” all potentially associated stations to be able to communicate with the access point. From the perspective of an associated station, operating at a lower power level may result in the station losing its channel to another station (a “hidden node”) that had been quiescent but suddenly becomes active, on the same channel, at a higher power level. To avoid that result, the station may operate at a high power level, even if not required under current conditions to reach the access point, to make sure that any hidden node is aware that the channel is in use.
Such power behavior by both access points and associated stations may lead to performance degradation, particularly in a network with multiple access points, some of which may have overlapping coverage areas (“overlapping BSSs” or “OBSSs”). First, there is the basic inefficiency of using more power than needed to accomplish a particular communication. Second, in an OBSS configuration, two access points with overlapping coverage areas may interfere with each other, in that stations within the overlap area may be unable to maintain a consistent link with one access point if the signal from another nearby access point is too strong. Third, the ability to perform Dynamic Clear Channel Assessment (“Dynamic CCA”) may be impaired as well.